Misdiagnosis of the presence and the identity of crystal species in joint space are often penalized with the incorrect treatment of the arthropathic condition. The existing diagnostic standard of polarized imaging lacks specificity and sensitivity and it is largely limited to microscopically visible birefringent crystals. In the current study we propose Raman spectroscopy as an alternative for diagnostic technology for improved identification of crystal species in joint spaces. In Raman spectroscopy molecular vibrations are triggered through laser excitation and the reflected light holds information on the identity as well as on the amount of species in the observed region. The technique is currently utilized for arthroscopic in vivo diagnosis of other diseases; thus, based on this clinical potential it would be worthwhile to explore its analytical and clinical feasibility towards the assessment of crystal species involved in arthropathic conditions. The first phase of the proposed exploratory study will reveal the identification thresholds of various crystals that can be detected by Raman spectroscopy. Synthetic analogs of monosodium urate, calcium pyrophosphate dihydrate, hydroxyapatite, octacalcium phosphate, tricalcium phosphate, calcium oxalate, cholesterol, cystine and xanthine will be mixed with healthy synovial fluid samples at various concentrations and these mixtures will be analyzed at the macro level to detect the cumulative signal emanating from crystals. We will attempt to lower the identification thresholds by employing surf ace-enhanced Raman spectroscopy and by principal component analysis of the spectral data. During the second phase synovial fluid samples will be taken from patients and the presence or absence of crystals will be confirmed via compensated polarized microscopy, X-ray diffraction and alizarin staining. Aliquots of these samples will be subjected to Raman analysis to determine whether Raman analysis can detect the presence and identity of crystals in clinical samples. If this exploratory study demonstrates that the analytical limits of Raman analysis suffice to cover clinical concentrations of crystal species than comprehensive clinical studies can be conducted to assess the specificity and the sensitivity of the technique finally leading to the development of an arthroscopic Raman device. [unreadable] [unreadable]